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A Pilot Framework and Gap Analysis Towards Developing a Fluvial Classification System in the Ross Sea Region Antarctica

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A Pilot Framework and Gap Analysis Towards Developing a Fluvial Classification System in the Ross Sea Region Antarctica PCAS 17 (2014/2015) Supervised Project A PILOT FRAMEWORK AND GAP ANALYSIS TOWARDS DEVELOPING A FLUVIAL CLASSIFICATION SYSTEM IN THE ROSS SEA REGION ANTARCTICA Lorna Louise Thurston Student ID: 12670481 Abstract: An integrated literature review has been undertaken with regards to the hydrological regime and fluvial geomorphology of the Ross Sea Region, Antarctica. The findings have been applied to develop a pilot framework for a process-based classification system of channels, ponds and lakes, and to identify gaps in knowledge that need to be addressed in order for the classification system to be developed further. The intention of the process-based classification system is that, once developed, it will be applied as a tool to help understand fluvial response to climate change and an increasing human footprint in the Ross Sea Region. In this regard, it would contribute towards a contemporary project - Assessing the Sensitivity of Dry Valleys to Change. It may also be useful for other applications, such as ecological research, and applicable to other regions of Antarctica. Several gaps in research have been identified that need to be addressed in order to integrate knowledge of the hydrological regime and fluvial morphology and subsequently develop a process-based classification system. In no particular order, these gaps include knowledge of: the spatial distribution of channel morphologies; fluvial morphological behaviour under heavily transport- and supply- limited conditions; the formation and desiccation of ponds, and their associated impact on the land’s surface; the significance, timing and origin of hill-slope processes; whether the spatial variability of melt, and the proportion of this melt that eventuates as surface flows, drive fluvial morphologies, or whether other processes exert a greater control; and whether events that are not directly climate/melt-driven, including when a glacier flows into and displaces a lake, jökulaups (ice-dam floods), and basal meltwater drainage of wet-based glaciers, have a transient or evolutionary effect on fluvial morphology. 1 CONTENTS 1. INTRODUCTION ................................................................................................................. 3 1.1 BACKGROUND ........................................................................................................... 3 1.2 PROPOSAL .................................................................................................................. 4 1.3 REPORT STRUCTURE .................................................................................................. 5 2. SITE DESCRIPTION: ROSS SEA REGION, ANTARCTICA .................................................... 5 3. ROSS SEA REGION HYDROLOGICAL SYSTEM OVERVIEW ............................................... 9 3.1 SIGNIFICANCE OF THE HYDROLOGICAL SYSTEM ....................................................... 9 3.2 A SUMMARY OF THE HYDROLOGICAL SYSTEM ......................................................... 9 4. ATMOSPHERE .................................................................................................................. 11 5. GLACIERS AND SNOW ...................................................................................................... 13 5.1 GLACIAL / INTERGLACIAL HYDROLOGICAL FLUCTUATIONS .................................... 13 5.2 SHORT-TERM FLUCTUATIONS OF GLACIERS AND SNOW PATCHES ........................ 14 5.3 ICE CLIFFS VS. GLACIERS’ SURFACES ........................................................................ 15 6. CRYOCONITE HOLES ........................................................................................................ 16 7. MELTWATER STREAMS .................................................................................................... 17 8. THE ONYX RIVER .............................................................................................................. 18 9. LAKES ............................................................................................................................... 20 9.1 DEFINING LAKES ...................................................................................................... 20 9.2 TAYLOR VALLEY LAKES ............................................................................................. 20 9.3 INPUTS AND OUTPUTS ............................................................................................ 21 9.4 DRIVERS OF LAKE LEVEL CHANGE ............................................................................ 21 10. PONDS ......................................................................................................................... 22 11. SUBSURFACE FLOWS ................................................................................................... 24 12. A PILOT FRAMEWORK FOR DEVELOPING A CLASSIFICATION SYSTEM ........................ 25 12.1 STREAMS AND RIVERS ......................................................................................... 25 12.2 PONDS AND CRYCONITE HOLES .......................................................................... 27 12.3 LAKES ................................................................................................................... 28 13. CONCLUSION ............................................................................................................... 28 14. REFERENCES ................................................................................................................ 29 2 1. INTRODUCTION 1.1 BACKGROUND Fluvial morphological classifications systematically identify water bodies, reaches or units with relatively homogenous morphologies in order to easily communicate information about their characteristics. They are based on the concept that fluvial geomorphology responds to changes in environmental forcing - natural or anthropogenic. Ultimately they seek to predict how a water body, reach or unit will respond over time to environmental forcing. They also provide a means for hydrological data to be extrapolated to different localities (Rosgen, 1994), although this requires considerable caution. Accordingly, such classifications assist in ecological, geological, engineering and resource management applications, investigations of channel response to climate change and human impact, and mass balance calculations. The advent of assigning and applying classifications is not new, with literature citing references at least as far back as 1899 when Davis divided streams into youthful, mature, and old age according to their relative stage of adjustment (McDavitt, 2004; Rosgen, 1994). Since this time, geomorphologial literature has been directed towards channel classifications, rather than classifications of other water bodies, which is likely because of their dynamic nature. Several classification systems concerning water chemistry / ecological health have been developed to assist with managing lakes (Salm, Saros, & Fritz, 2009; Uttormark & Wall, 1975; Wagner, Bremigan, & Cheruvelil, 2007), but geomorphological classifications have not eventuated as they have for channels. This is attributed to lakes considerably slower rate of morphological change, comparative to channels, which are dynamic hydrological features. Channel classification systems have progressed considerably since Davis’s simple classification. Horton (1945) paved the way for quantitative fluvial geomorphology, introducing the concept of stream ordering which was developed further by Strahler (1957). Under this system, first order streams emerge at the headwaters of a catchment and orders progressively increasing at each confluence. Broad-ranging descriptions of channel form were also published – starting with simple classifications such as straight, meandering and braided (Leopold and Wolman, 1957), and progressing to more detailed descriptions (Kellerhals et al., 1976). Rosgen’s (1994) classification system, which establishes quantitative groupings of homogenous reaches in natural rivers, has been widely applied. It focuses on providing a broad geomorphic characterization (Level I) and morphological description (Level II) of channels. Eight generalized categories of “stream types” are identified using longitudinal profiles, valley and channel cross-sections, and plan-view patterns. Streams are further categorized into 42 types based on discreet slope ranges and dominant channel-material particle sizes. More recently the focus has been on classification systems that couple morphology and process in specific environments. Montgomery and Buffington’s (1997, pp. 1) process-based system identifies seven distinct mountain reach types, including: “colluvial, bedrock, and five alluvial channel types: cascade, step pool, plane bed, pool riffle, and dune ripple”. This allows dominant channel forming mechanisms to be 3 identified based on fluvial morphology, which may be hillslope processes (supplying the system) or fluvial processes (transporting material in the system). Although the hydrological regime of Antarctica has been investigated towards ecological ends (Fountain et al., 1999; Gooseff et al., 2011), a comprehensive classification system for fluvial systems has not been developed for polar environments, which presents a significant gap in knowledge. It is proposed that such a classification system would assist with the broad-ranging applications listed in the opening paragraph. As Antarctica is the last place on earth to feel human impact, and is sensitive to climate forcing (as described in
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